From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD040C63777 for ; Thu, 3 Dec 2020 12:17:44 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1591C20872 for ; Thu, 3 Dec 2020 12:17:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1591C20872 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:55086 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kknYM-00032u-Jx for qemu-devel@archiver.kernel.org; Thu, 03 Dec 2020 07:17:42 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:38342) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kknXP-0002Yb-Fc for qemu-devel@nongnu.org; Thu, 03 Dec 2020 07:16:43 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48009) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kknXM-0004wP-JX for qemu-devel@nongnu.org; Thu, 03 Dec 2020 07:16:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606997799; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=bxYYgHgg0XtLsCg9fWS+ePrcErrism2Dmqtwuo2d014=; b=W1CnAHIbMTvjtN0bShB/DNzLBhZK5LpKP93a3TVOO1aptlgKukFzZ8hTxz/cQbIxpo/wrH 8XJG9CnYpEzQfEwEcnFH56fVsnh/jqyUHcn5+uofp9rWU/fkDNaScAxnTEivO7xBEYhZpH Ks86JaJFLgpPg+8bAqGZxK5H9C/lPTs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-565-XQMr27HbPAOKXyIlljeGoQ-1; Thu, 03 Dec 2020 07:16:35 -0500 X-MC-Unique: XQMr27HbPAOKXyIlljeGoQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C45D18797DD for ; Thu, 3 Dec 2020 12:16:34 +0000 (UTC) Received: from redhat.com (ovpn-115-57.ams2.redhat.com [10.36.115.57]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A3B1E19C46; Thu, 3 Dec 2020 12:16:29 +0000 (UTC) Date: Thu, 3 Dec 2020 12:16:24 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: "Michael S. Tsirkin" Subject: Re: [PATCH v2 01/27] migration: Network Failover can't work with a paused guest Message-ID: <20201203121624.GG2952498@redhat.com> References: <20201202105515.GD2360260@redhat.com> <20201202061641-mutt-send-email-mst@kernel.org> <20201202112639.GE2360260@redhat.com> <20201202063656-mutt-send-email-mst@kernel.org> <20201202120121.GF2360260@redhat.com> <20201203061907-mutt-send-email-mst@kernel.org> <20201203113253.GD2952498@redhat.com> <20201203063452-mutt-send-email-mst@kernel.org> <20201203114341.GB2919@work-vm> <20201203070339-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: <20201203070339-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.495, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Eduardo Habkost , Juan Quintela , Jason Wang , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Dec 03, 2020 at 07:11:17AM -0500, Michael S. Tsirkin wrote: > On Thu, Dec 03, 2020 at 11:43:41AM +0000, Dr. David Alan Gilbert wrote: > > Another way to solve this would be to remove the unplugging from the > > migration layer and leave it as a problem for the management layer to do > > the unplug. > > Daniel described the problem with modular management tools which expect > pausing or slowing down guest to cause migration to converge. > > Point is, it actually *will* make it converge but only if you > pause it after unplug. > > As it is, these tools fundamentally can not handle failover > requiring guest cooperation. Moving code between layers won't help. > Introducing failure modes as this patch does won't help either > especially since Daniel wrote there are countless tools like this. > We just break them all but have no resources to fix them, > this does not help at all. > > We can just leave the situation as is. > > Or if we do want to be nice to these tools, how about we > unpause the guest until unplug, then pause it again? > This actually addresses the problem instead of > shifting the blame, does it not? This is a very bad idea because it changes the execution status of the guest behind the apps/admins back, and that cannot be assumed to be a safe thing todo. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|